“The erosion of Exposition Park’s public open space continues.” So wrote urban planner Alan Loomis nearly 15 years ago, in an essay published by the Los Angeles Forum for Architecture and Urban Design.

That was before the Natural History Museum, born as thecounty museum and long the park’s anchor cultural tenant, ditched one expansion plan and built another; before the architecture firm Morphosis added an elementary school, wrapped in its signature slashing forms, near the northeast corner of the park; before USC took formal control of the Coliseum, with plans to modernize it; before the space shuttle Endeavour arrived at the California Science Center, with a new glass pavilion planned to house it; and before Welton Becket’s Sports Arena was demolished to make way for a soccer stadium.

With the news Tuesday that George Lucas will be building a billion-dollar museum of “narrative art” just west of the Coliseum, choosing that site over a competing one on Treasure Island in San Francisco Bay, the balance in Exposition Park has tipped once more from open space toward architecture, from protecting to building. The museum — a long, white, aerodynamic form that will seem to float above the surface of the park — will be designed by young Chinese architect Ma Yansong and is expected to open in 2021.

You could argue, in other words, that a lot has changed in Exposition Park in a generation or that nothing has. Even as more trophy buildings and cultural attractions are squeezed inside its 160 acres, connected by the Expo Line to the regional rail network, it retains its traditional usefulness for the city in both political and emblematic terms.

It is a wellspring Los Angeles mayors can always dip into when making their most ambitious civic pitches. (Let’s get one of those retired space shuttles for our very own! And the NFL — again! And a third Olympics!) It is also a stage where the region’s oldest morality play, the one casting Southern California as a paradise lost, a region whose beauty and natural resources are perennially threatened by overzealous development, is mounted, like the “Ramona” pageant, again and again.

George Lucas' Museum of Narrative Art will be built in Los Angeles, the project's directors have announced. The $1-billion Exposition Park museum will be funded by Lucas, the creator of "Star Wars."

George Lucas' Museum of Narrative Art will be built in Los Angeles, the project's directors have announced. The $1-billion Exposition Park museum will be funded by Lucas, the creator of "Star Wars."

What Exposition Park isn’t, in either case, is a carefully guarded open space, though it sits in a part of the city, just south of USC, that is woefully park-poor according to every available metric. Instead it’s a near-perfect symbolic landscape for a city that has typically been more interested in appearing nimble and forward-looking than meticulously planned — more interested in choosing the City of the Future label than the City Beautiful one.

The pitch Mayor Eric Garcetti made to Lucas and his wife, Mellody Hobson, had everything to do with a streamlined political and construction process. This was in large part meant to distinguish L.A. from San Francisco and Chicago, cities where Lucas had already tried and failed to get the museum approved. (The Treasure Island proposal was a second Bay Area attempt.)

But it also played to — and in the end confirmed — certain ideas Los Angeles has about itself, that it’s a city without a robust culture of civic engagement, that builds first and asks questions later, that pounces on opportunities like the Lucas Museum of Narrative Art rather than debating them.

I’m not wowed by what we know of Lucas’ collection. It seems to promise an awkward marriage between Hollywood memorabilia and easy-to-swallow figurative art by Norman Rockwell and others. (The idea that the museum’s arrival will boost L.A.’s cultural reputation is — to be plain — a joke.) The building proposed to house it has more potential but will have to overcome a certain sleek placelessness in the initial designs.

Nor do I think we should put much stock in the argument that Lucas isn’t really vacuuming up open space because the land he’ll be building on is now covered with parked cars. Surface parking lots are easily converted into usable green space; and demand for parking is set to dramatically decline over the next few decades, according to most urban planners. In any long-term calculus, giving Lucas these lots is basically the same as giving him grassy fields.

But I’ve also found it hard to work up much outrage about the Lucas deal. Certainly it would be tough to argue that any of the various master plans developed over the decades for Exposition Park — whose land is primarily owned by the state and controlled by a nine-member board of directors — has ever been worth the paper they’ve been printed on, so easily have they been tossed aside when a proposal like this one comes along. Support for the Lucas plan has been so uniformly strong among local power brokers that even USC President C. L. Max Nikias, who on his own campus enforces a strict architectural requirement that every new building look old, signed on to help promote it.

For most of the public, admittedly, Exposition Park exists less as a green enclave, some quiet escape from the city, than as a collection of civic, cultural and athletic venues, the more populist and crowd-pleasing the better.

Would it be more faithful to the history and mission of Exposition Park to oppose the museum or welcome it? I’m not sure there’s an easy answer to that question.

There is irony in all of this, of course, both in historical terms and contemporary ones. Much of Exposition Park was originally laid out a century ago following City Beautiful principles, though beyond the Rose Garden it can be tough to recognize that these days. And Garcetti’s pitch about a fast-moving, quick-to-build Los Angeles is true mostly just in relative terms, in comparison with Chicago and San Francisco, cities with civic organizations that guard their remaining open space as actively as any in the world.

Examined next to the L.A. of the postwar decades, the contemporary city is sluggish and crowded, a place where the approvals process for a restaurant or corner store can seem endless and where, more to the point, the unbuilt land available for projects like Lucas’ is shrinking by the day.

And I can count on one hand the number of architecturally innovative civic or cultural landmarks planned and completed in the last decade. Despite Garcetti’s pitch, L.A. hasn’t been an especially sympathetic city for architectural experimentation since the 1990s, though the current construction boom has begun to see the pendulum swing back a bit.

What the Lucas Museum and soccer-stadium plans say about Exposition Park’s place in the city has more to do with the shifting trajectory of development and investment than about L.A.’s hospitality to adventurous architecture. After decades during which the region concentrated mostly on ways to expand at the edges, it is now folding back on itself, growing denser and building infill, with activity in and around downtown particularly intense. That makes the target on Exposition Park’s remaining empty space only bigger and more obvious.

At the same time, thanks to recently approved Measure A and a growing pot of so-called Quimby funds — fees collected from developers to pay for new open space — the city and county of Los Angeles are at the moment planning and opening more parks than they have for many years.

None of course will have the size or historical and geographical significance of Exposition Park, which sits at a crucially important nexus between east and west and between downtown and South L.A. And yet as long as there are any slivers of open space left in the park, it seems destined to continue operating more as a tabula rasa in the civic imagination than a fixed, finished landscape that calls out for protection.

That makes Exposition Park a kind of throwback — an anomaly in the Los Angeles now taking shape but a deeply familiar civic landscape in historical terms. For better and worse, the park is one territory where L.A.’s reputation as an opportunistic city above all, a city proudly on the make, has refused to fade.

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Justin Chang and Glenn Whipp talk about the top contenders of the awards season, including "Call Me by Your Name" and "The Florida Project."

Justin Chang and Glenn Whipp talk about the top contenders of the awards season, including "Call Me by Your Name" and "The Florida Project."

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Justin Chang and Glenn Whipp talk about the top contenders of the awards season, including "Call Me by Your Name" and "The Florida Project."

Justin Chang and Glenn Whipp talk about the top contenders of the awards season, including "Call Me by Your Name" and "The Florida Project."

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Justin Chang and Glenn Whipp on what critics awards mean for the Oscars, factoring in the academy's expanding membership.

Justin Chang and Glenn Whipp on what critics awards mean for the Oscars, factoring in the academy's expanding membership.

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Two men return home from World War II to work on a farm, where they struggle to deal with racism and adjusting to life after war in "Mudbound." Video by Jason H. Neubert

Two men return home from World War II to work on a farm, where they struggle to deal with racism and adjusting to life after war in "Mudbound." Video by Jason H. Neubert

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It's quite the challenge trying to interview the energetic child stars of "The Florida Project."

It's quite the challenge trying to interview the energetic child stars of "The Florida Project."

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Director Dee Rees talks about casting Mary J. Blige, Carey Mulligan and Jason Mitchell for her film "Mudbound." After loving Mitchell's performance in "Straight Outta Compton," Rees said, "I'd be so lucky to get him in my film."

Director Dee Rees talks about casting Mary J. Blige, Carey Mulligan and Jason Mitchell for her film "Mudbound." After loving Mitchell's performance in "Straight Outta Compton," Rees said, "I'd be so lucky to get him in my film."